High‐Efficiency Photothermal Water Evaporation using Broadband Solar Energy Harvesting by Ultrablack Silicon Structures

Abstract

Development of broadband absorption materials for solar energy harvesting is an important strategy to address global energy issues. Herein, it is demonstrated that an ultrablack silicon structure with abundant surface texturing can absorb about 98.7% solar light within the wavelength range of 300 to 2500 nm, i.e., a very large range and amount. Under 1 sun irradiation, the ultrablack silicon sample's surface temperature can increase from 21.2 to 51.2 °C in 15 min. During the photothermal water evaporation process, the ultrablack silicon sample's surface temperature can still reach a highest temperature of 43.2 °C. The average photothermal conversion efficiency (PTCE) can be as high as 72.96%. The excellent photothermal performance to the excellent light‐trapping ability of the pyramidal surface nanostructures during solar illumination, which leads to extremely efficient absorption of light, is attributed. In addition, the large water contact area also enables fast vapor transport. The stability of the photothermal converter is also examined, presenting excellent structure and performance stabilities over 10 cycles. This indicates that the ultrablack Si absorber can be a promising photothermal conversion material for seawater desalination, water purification, photothermal therapy, and more.

Photothermal Effects and Heat Conduction in Nanogranular Silicon Films

“…In addition to assessment of thermal properties, the PT effects are also utilized in a variety of critical applications ranging from photothermal imaging [ 11 ], PT therapy [ 12 ] to hyperthermia for cancer therapy and theranostics [ 13 ]. In particular, porous Si (Por-Si) and Si NPs are also attractive for PT therapeutic applications due to their biocompatibility, biodegradability, high surface area and controllable pore diameter [ 14 ].…”

Tailoring Patterned Visible-Light Scattering by Silicon Photonic Crystals

“…FDTD simulations were performed by using the commercial software FDTD solutions (Lumerical Solutions Inc.). 33 All the parameters for the models are based on the experimental results with a minor approximation. For Si NPs, the radius and the height are 260 and 530 nm, respectively.…”

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A Review on Photothermal Conversion of Solar Energy with Nanomaterials and Nanostructures: From Fundamentals to Applications

“…Micro/nanostructured materials include black carbon-based materials, black silicon, black GaAs, and other black materials. [21,31,34,52,53,[94][95][96][97][98][99] Generally, bulk materials tend to have a limited emissivity. For example, a graphite sheet without micro/nanostructures has an emissivity of ≈0.85, which is not beneficial for solar energy harvesting.…”

“…[29,[37][38][39][40][41][42][43][44] Among all the applications, photothermal water evaporation for desalination and water purification has attracted the most attention, owning that freshwater can be directly produced by only using solar energy and it can address the freshwater shortage challenge for many countries. [27,32,33,[45][46][47][48][49][50][51][52][53] However, the research focusing on other applications has attracted less attention than photothermal water evaporation, which should also be taken equally important attention for making the most of solar energy. For example, photothermal catalysis for H 2 generation and CO 2 reduction can be applied to convert solar energy into chemical energy under high concentrated solar intensity, but the efforts are still far from enough.…”